During the route discovery process, each node receiving the route request packet (RReq) will retransmit it exactly once. A distant neighbor may accidentally receive/loose the only RReq and use it to announce a new route, although that link is inferior/superior for route reply packets (RRep) or actual message routing. Overall, the constructed route may be far from the optimal. All existing route discovery schemes (including DSR/AODV) apply retransmission during route discovery exactly once (1R). Based on a realistic physical layer model, we propose two new route discovery schemes: n-retransmission (nR, retransmitting exactly n times) and n-retransmission c-reception (ncRR), retransmitting until we either reach a total of n own retransmissions or c copies from neighbors are heard. We compare our two new scheme with the traditional one, under otherwise identical conditions (same metric, same packet reception probability on each link) and the same choices about possibly retransmitting again upon discovering a better route (R+) or discarding it (R1), generating route reply packet for every received RRep (B*), or for first and better discovered routes only (B2), and retransmitting RRep exactly once (A1), up to a maximum of three times (A3), or optimally u times decided by link quality (Au). Experimental results show that the proposed ncRR scheme (for n=2 and c=3 or c=4) achieves the best tradeoff between quality of route, success rate and message overhead in the route discovery process, followed by the nR scheme, and both of them are superior to the existing traditional schemes.

During the route discovery process, each node receiving the route request packet (RReq) will retransmit it exactly once. A distant neighbor may accidentally receive/loose the only RReq and use it to announce a new route, although that link is inferior/superior for route reply packets (RRep) or actual message routing. Overall, the constructed route may be far from the optimal. All existing route discovery schemes (including DSR/AODV) apply retransmission during route discovery exactly once (1R). Based on a realistic physical layer model, we propose two new route discovery schemes: n-retransmission (nR, retransmitting exactly n times) and n-retransmission c-reception (ncRR), retransmitting until we either reach a total of n own retransmissions or c copies from neighbors are heard. We compare our two new scheme with the traditional one, under otherwise identical conditions (same metric, same packet reception probability on each link) and the same choices about possibly retransmitting again upon discovering a better route (R+) or discarding it (R1), generating route reply packet for every received RRep (B*), or for first and better discovered routes only (B2), and retransmitting RRep exactly once (A1), up to a maximum of three times (A3), or optimally u times decided by link quality (Au). Experimental results show that the proposed ncRR scheme (for n=2 and c=3 or c=4) achieves the best tradeoff between quality of route, success rate and message overhead in the route discovery process, followed by the nR scheme, and both of them are superior to the existing traditional schemes.

The wireless network design problem (WNDP) considers how best to place a set of antennas so the antennas can send and receive the maximum possible amount of data subject to network-performance constraints (e.g., channel-availability constraints). To date, little research has considered how to choose the network-antenna layout that maximizes throughput under these conditions. Also, past research has mainly investigated networks with omnidirectional antennas only, not other types of antennas. A bi-level mixed-integer program is constructed to solve this problem using a cutting-plane approach. The data produced from this model demonstrate an extension of the WNDP under more realistic conditions than have been simulated previously. The questions answered by this research are as follows: (1) what are the effects on network throughput of utilizing directional or sectored antennas instead of omnidirectional antennas, and (2) what is the maximum possible throughput when imposing constraints related to differing interference types and channel availability?

No description available.

Wireless operators adopting third-generation (3G) technologies and those migrating from second-generation (2G) to 3G face a number of challenges related to traffic modeling, demand characterization, and performance analysis, which are key elements in the processes of designing, dimensioning and optimizing their network infrastructure. Traditional traffic modeling assumptions used for circuit-switched voice traffic no longer hold true with the convergence of voice and data over packet-switched infrastructures. Self-similar models need to be explored to appropriately account for the burstiness that packet traffic is expected to exhibit in all time scales. The task of demand characterization must include an accurate description of the multiple user profiles and service classes the network is expected to support, with their distinct geographical distributions, as well as forecasts of how the market should evolve over near and medium terms. The appropriate assessment of the quality of service becomes a more complex issue as new metrics and more intricate dependencies have to be considered when providing a varying range of services and applications that include voice, real-time, and non-real time data. All those points have to be considered by the operator to obtain a proper dimensioning, resource allocation, and rollout plan for system deployment. Additionally, any practical optimization strategy has to rely on accurate estimates of expected demand and growth in demand. In this research, we propose a practical framework to characterize the traffic offered to multimedia wireless systems that allows proper dimensioning and optimization of the system for a particular demand scenario. The framework proposed includes a methodology to quantitatively and qualitatively describe the traffic offered to multimedia wireless systems, solutions to model that traffic as practical inputs for simulation analysis, and investigation of demand-sensitive techniques for system dimensioning and performance optimization. We consider both theoretical and practical aspects related to the dimensioning of hybrid traffic (voice and data) for mobile wireless networks. We start by discussing wireless systems and traffic theory, with characterization of the main metrics and models that describe the users’ voice and data demand, presenting a review of the most recent developments in the area. The concept of service class is used to specify parameters that depend on the application type, performance requirements and traffic characteristics for a given service. Then we present the concept of “user profile,“ which ties together a given combination of service class, propagation environment and terminal type. Next, we propose a practical approach to explore the dynamics of user geographical distribution in creating multi-service, multi-class traffic layers that serve as input for network traffic simulation algorithms. The concept of quality-of-service (QoS) is also discussed, focusing on the physical layer for 3G systems. We explore system simulation as a way to dimension a system given its traffic demand characterization. In that context, we propose techniques to translate geographical distributions of user profiles into the actual number of active users of each layer, which is the key parameter to be used as input in simulations. System level simulations are executed for UMTS systems, with the purpose of validating the methodology proposed here. We complete the proposed framework by applying all elements together in the process of dimensioning and optimization of 3G wireless networks using the demand characterization for the system as input. We investigate the effects of modifying some elements in the system configuration such as network topology, radio-frequency (RF) configuration, and radio resource management (RRM) parameters, using strategies that are sensitive to traffic geographical distribution. Case study simulations are performed for Universal Mobile Telecommunications System (UMTS) networks, and multiple system variables (such as antenna tilts, pilot powers, and RRM parameters) are optimized using traffic sensitive strategies, which result in significant improvements in the overall system capacity and performance. Results obtained in the case studies, allied to a generic discussion of the trade-offs involved in the proposed framework, demonstrate the close dependence between the processes of system dimensioning and optimization with the accurate modeling of traffic demand offered to the system. / Ph. D.

Solar Wireless Networked Control Systems (SWNCS) are a style of distributed control systems where sensors, actuators, and controllers are interconnected via a wireless communication network. This system setup has the benefit of low cost, flexibility, low weight, no wiring and simplicity of system diagnoses and maintenance. However, it also unavoidably calls some wireless network time delays and packet dropout into the design procedure. Solar lighting system offers a clean environment, therefore able to continue for a long period. SWNCS also offers multi Service infrastructure solution for both developed and undeveloped countries. The system provides wireless controller lighting, wireless communications network (WI-FI/WIMAX), CCTV surveillance, and wireless sensor for weather measurement which are all powered by solar energy.

With advances in wireless technology and mobile devices, the number of mobile users using multimedia services has increased significantly in recent years. Mobile devices can be connected and roam on heterogeneous wireless networks. The IEEE 802.21 group has designed a Media Independent Handover (MIH) standard to ensure seamless Vertical Handover (VHO) in heterogeneous networks. However, the standard currently depends on features of the network (e.g. the type of network and available bandwidth) to achieve seamless VHO. This approach is limited, as it does not consider how a Quality of Experience (QoE) can be provided and maintained for customers when delivering multimedia services in heterogeneous wireless networks. The aim of the project is to develop a novel QoE-driven VHO management framework for providing and maintaining an appropriate level of QoE of multimedia services as the mobile user’s actual requirements in heterogeneous wireless networks. A QoE-driven VHO algorithm is more efficient for maintaining this acceptable QoE of multimedia services than traditional network-based or QoS-based VHO algorithms. There are three main contributions during this project. Firstly, A thorough evaluation of the performance of voice and video services via Skype was carried out in terms of the QoE metric (i.e. MOS). This work identified the impact of video content and packet loss on the QoE metric for voice and video communication services over wireless networks. Secondly, a QoE-driven VHO algorithm was developed to provide and maintain an acceptable QoE of mobile video services for mobile users. Compared to a traditional network-based VHO algorithm, this algorithm can provide better QoE and maintain acceptable QoE. Lastly, the User-centric QoE-driven (UCQoE) VHO framework to provide satisfactory QoE of multimedia services according to the mobile user’s requirements. The framework allows users to set their own preferences (e.g. quality-guarantee or cost-free) and carry out VHO operations accordingly. The evaluation showed that the proposed framework can provide a better QoE for delivered video services than QoS-based and network-based VHO algorithms. Furthermore, the proposed framework can be used to avoid unnecessary cost of mobile data when the option of cost-free is preferred by the user. During this project, three international conference papers had been published and a journal paper has been submitted to IEEE Transactions on Mobile Computing. The main contribution-UCQoE VHO management framework can be developed to maintain QoE of all mobile services in the future.

" IEEE 802.11 wireless access points (APs) act as the central communication hub inside homes, connecting all networked devices to the Internet. Home users run a variety of network applications with diverse Quality-of-Service requirements (QoS) through their APs. However, wireless APs are often the bottleneck in residential networks as broadband connection speeds keep increasing. Because of the lack of QoS support and complicated configuration procedures in most off-the-shelf APs, users can experience QoS degradation with their wireless networks, especially when multiple applications are running concurrently. This dissertation presents CATNAP, Classification And Treatment iN an AP , to provide better QoS support for various applications over residential wireless networks, especially timely delivery for real-time applications and high throughput for download-based applications. CATNAP consists of three major components: supporting functions, classifiers, and treatment modules. The supporting functions collect necessary flow level statistics and feed it into the CATNAP classifiers. Then, the CATNAP classifiers categorize flows along three-dimensions: response-based/non-response-based, interactive/non-interactive, and greedy/non-greedy. Each CATNAP traffic category can be directly mapped to one of the following treatments: push/delay, limited advertised window size/drop, and reserve bandwidth. Based on the classification results, the CATNAP treatment module automatically applies the treatment policy to provide better QoS support. CATNAP is implemented with the NS network simulator, and evaluated against DropTail and Strict Priority Queue (SPQ) under various network and traffic conditions. In most simulation cases, CATNAP provides better QoS supports than DropTail: it lowers queuing delay for multimedia applications such as VoIP, games and video, fairly treats FTP flows with various round trip times, and is even functional when misbehaving UDP traffic is present. Unlike current QoS methods, CATNAP is a plug-and-play solution, automatically classifying and treating flows without any user configuration, or any modification to end hosts or applications. "

Multi-hop wireless networks have been widely considered as promising approaches to provide more convenient Internet access for their easy deployment, extended coverage, and low deployment cost. However, providing high-speed and reliable services in these networks is challenging due to the unreliable wireless links, broadcast nature of wireless transmissions, and frequent topology changes. On the other hand, network coding (NC) is a technique that could significantly improve the network throughput and the transmission reliability by allowing intermediate nodes to combine received packets. More recently proposed symbol level network coding (SLNC), which combines packets at smaller symbol scale, is a more powerful technique to mitigate the impact of lossy links and packet collisions in wireless networks. NC, especially SLNC, is thus a particular effective approach to providing higher data rate and better transmission reliability for applications such as mobile content distribution in multihop wireless networks. This dissertation focuses on exploiting NC in multihop wireless networks. We studied the unique features of NC and designed a suite of distributed and localized algorithms and protocols for content distribution networks using NC and SLNC. We also carried out a theoretical study on the network capacity and performance bounds achievable by SLNC in mobile wireless networks. We proposed CodeOn and CodePlay for popular content distribution and live multimedia streaming (LMS) in vehicular ad hoc networks (VANETs), respectively, where many important practical factors are taken into consideration, including vehicle distribution, mobility pattern, channel fading and packet collision. Specifically, CodeOn is a novel push based popular content distribution scheme based on SLNC, where contents are actively broadcast to vehicles from road side access points and further distributed among vehicles using a cooperative VANET. In order to fully enjoy the benefits of SLNC, we proposed a suite of techniques to maximize the downloading rate, including a prioritized and localized relay selection mechanism where the selection criteria is based on the usefulness of contents possessed by vehicles, and a lightweight medium access protocol that naturally exploits the abundant concurrent transmission opportunities. CodePlay is designed for LMS applicaitions in VANETs, which could fully take advantage of SLNC through a coordinated local push mechanism. Streaming contents are actively disseminated from dedicated sources to interested vehicles via local coordination of distributively selected relays, each of which will ensure smooth playback for vehicles nearby. CodeOn pursues a single objective of maximizing downloading rate, while CodePlay improves the performance of LMS service in terms of streaming rate, service delivery delay, and bandwidth efficiency simultaneously. CodeOn and CodePlay are among the first works that exploit the features of SLNC to simplify the protocol design whilst achieving better performance. We also developed an analytical framework to compute the expected achievable throughput of mobile content distribution in VANETs using SLNC. We presented a general analytical model for the expected achievable throughput of SLNC in a static wireless network based on flow network theory and queuing theory. Then we further developed the model to derive the expected achievable accumulated throughput of a vehicle driving through the area of interest under a mobility pattern. Our proposed framework captures the effects of multiple practical factors, including vehicle distribution and mobility pattern, channel fading and packet collision, and we characterized the impacts of those factors on the expected achievable throughput. The results from this research are not only of interest from theoretical perspective but also provide insights and guidelines on protocol design in SLNC-based networks.

Because of the popularity of wireless communication technologies, people can access servers without the restriction of place and time. With the rapid development of mobile devices, such as smart phones and iPads, the frequency of wireless networks have increased. Roaming services ensure service provision without location constraints. A secure roaming authentication protocol is critical for the security and privacy of users when accessing services by roaming. It ensures the authenticity of mobile users, and foreign and home servers. After authentication, the session key for the mobile user and the foreign server is established for secure communication. In addition, a secure roaming protocol may provide anonymity for mobile users. When the mobile user requests a service, the server is unable to identify two requests from the same user. For the current anonymous authentication protocols, the foreign server must fulfill the revocation check by the computation linear to the number of revoked users. It makes the protocol infeasible in practical environments. This thesis proposes a strong anonymous authentication protocol, using two-stage authentication, in which the home server is involved in the initial authentication to eliminate the revocation list and issues a timely anonymous credential for subsequent authentication after successful authentication. It reduces the computation costs for the revocation check and minimizes the size of the revocation list. Finally, this thesis also provides security proofs and comparisons of the proposed authentication mechanism.